Selmeroid Build

[jeffhigh]

Time for something different for me
Going from Falcate bracing to ladder bracing on this one
Back and sides, some of Tim's blackwood from the last special
Jointed with HHG and tape method

[jeffhigh]

Spent most of my spare time this week building mould and bending form

[jeffhigh]

And bending this morning

[jeffhigh]

Well with two broken sides at the horn, this blackwood is telling me it does not want to be a selmer venetian cutaway.
The first time I thinned the cutaway area to 1.6mm and the second to 1.2.
So now it is a florentine.

[J.F. Custom]

Bugger

Still, I look forward to the florentine selmer!

Assume you bent with just water? I wonder if some veneer softener may have helped, of course, that is hindsight. Some blackwood I've had has bent easily - even around the very tight venetian in my bouzouki design. Whereas other pieces have failed on the same bend. I used some softener when bending some ringed Gidgee I had though as it just seemed too brittle to want to flex at all from the get go. It worked - bent fine around a Tenor uke profile.

Speaking of, I can't help but notice what appears to be a small breeding ground for ukes in the background... Can you tell us more about those too? What is the dark topped one - Wenge? Ziricote? Macassar even?? Hard to gauge from that little glimpse, but it looks good with the contrasting shell.

Jeremy.

[Mike Thomas]

Yes Jeff, I was wondering how you would go with that. Even with laminated sides (4 epoxied laminations of .6mm blackwood veneer), in a vacuum bag and bent to the mould whilst the epoxy was still wet, didn't easily conform to the shape. I finally managed it, after a couple of trys, but not without a lot of clamps and shaped cauls. Nick has done it though, more than once, but I can't remember offhand what timber he was using

[Mike Thomas]

And I was looking forward to a falcate braced Selmer.

[jeffhigh]

Ah yes the ukes, must finish them I kinda lost momentum. the dark faced one is sinker redwood.

I think there might just have been too much runout on the blackwood, but maybe I would have done better on the iron rather than form and blanket, and veneer softener would definitely have helped.

If I do another and try for venetian, I'll probably use Indian rosewood...

Whilst I love the results with the last three falcates I have built, I think the selmer tailpiece/floating bridge arrangement works better structurally with the ladder bracing.

[J.F. Custom]

Wow - sinker eh? I didn't guess that from the glimpse.

Anyway, sorry for the sidetrack - back to the Selmeroid build log now

Jeremy.

[Nick]

Nick has done it though, more than once, but I can't remember offhand what timber he was using

I've done it with high figure Blackwood but I've bent by hand around an iron, I believe this method (in this case) allowed me some leeway, as soon as there was the slightest hint of a crack at a cross grain I let the side cool then actually put the iron on the outside of the bend & 'pushed' the offending crossgrain back into shape (marked the offending crack so I could wick in CA later), allowed to cool again then resumed the bending slightly ahead of the last point.
It's tricky but with a bit of time and copious amounts of stop starting & observing the bend I managed to coax the Blackwood into the tight radius these things require. But good recovery Jeff, I imagine a florentine would suit these quite well.

[ozwood]

Hi Jeff.

I once sprayed some veneer softener , from carbatec on some blackwood left it for an hour and cold bent it ! , it works best on porous woods , and the blackwood result was the best i have had yet, Just a thought for next time.

Cheers,

[auscab]

Hi Jeff, It would be interesting to know how you tried to pull the steel slat around the horn. I would think if the slat was under tension ( say 20 to 30 kg , at a guess ) at each moment as it went around the horn , it would be the perfect way to do it .

[jeffhigh]

I have not got it set up for tension on the slat. That would have helped but I probably needed the veneer softener as well.
I guess I was just too optomistic thinking I would be fine with the reduced thickness.
Live and learn....

[jeffhigh]

Well I got the Top built and attached to the sides.
I used a fairly sharp pliage bent on my Ibex iron, tapering to nothing at the edge then jointed while supported at this angle.
I used 19mmX9.5 braces more favino than selmer (skipped the 5th brace and used reinforcement beside the soundhole rather than the spreadout selmer style)

Sorry no pics at the moment, my camera is out

Anyhow this thing is super rigid, it will not move at all with finger pressure at the bridge area. and is giving a resonance of around 300hz when tapped at the bridge area.
Is this to be expected or do I need to do a bit of brace trimming before the back goes on?
Nick?

[Nick]

The nature of the top's various bends & curves leads to a strong structure Jeff which is why these can afford to have a thinner top thickness than a flatty (typically 70-80 thou) and only ladder bracing, even then it's still remarkably strong as it has to resist the downward force of the strings.
I like a little flex at the bridge position,I've never measured it so I couldn't give you exact figures, I go more by what I'm feeling under my thumb but I would guess it to be in the 2-2.5mm range? The Favino I've never had much experience with so I'm not familiar with how much more or less flex these would have but obviously stiffer if the bracing is higher which I imagine would give it more top end to cut through but it's a fine balance between giving the sound some cut & killing it altogether!

[jeffhigh]

I'm just using the 19mm high braces as called up in the collins book and plan, and I am down to about 2.2mm allowing for some thinning later
I'm only judging by pushing with my thumb too, but I would put it at less than 1/2mm

Do you use that 19mm as a starting point and take it down a bit?

[Nick]

Do you use that 19mm as a starting point and take it down a bit?

The first one I built I left it at that simply because I was unsure exactly what it was I was trying to achieve so I thought "Stick to the instructions" but subsequent builds have involved some 'tweaking' of brace heights but only in the order of a mm or less or if you wanted to retain the strength through the bulk of the brace, take a bit out of the end scallops. There's quite a downward force the whole structure has to counteract especially if you are building the longer scale Petite Bouche & eliminating the 5th brace. I'd be aiming for a bit more flex than 0.5mm but even bringing the soundboard down that last little bit may loosen it some.

[jeffhigh]

Thanks Nick, that gives me something to go on,
My gut is telling me the braces are too stiff, I'll probably tweak them a bit then see how I go after finish sanding.
I guess I can always subcontract any final brace shaping to my gynocologist mate.

[jeffhigh]

Braced, and box assembled

[jeffhigh]

Front and Back

[jeffhigh]

I brought the braces down to 17mm high and with a bit longer tapering at the ends before closing, still very stiff.
Tapping at 108/ 268 HZ air and top monopole

[jeffhigh]

Neck and body united temporarily
Now to scraping sanding and polishing

[Nick]

Looking like a cracker at the moment Jeff, can only get even sweeter from here on in! What tuners did you end up going with? The ones you have here certainly look smart

[jeffhigh]

Just base grade Rubners, brass,hauser shape baseplate,open gears no engraving

[Mike Thomas]

Looking good Jeff. Do you know yet the likely height of the bridge?